Reference Michigan Gunsmiths from the 18th through the early 20th Centuries, James Kelly and Dorr N. Wiltse, privately published.
Now that I've got in my commercial, if I can figure out how to use some photo sevice I suppose I could post a picture or two. Not sure that I have any showing exactly what you need. Pin goes from some fraction of an inch from the back end of the toe plate, to near bottom of buttplate. At an angle, you might say.
I still would use soft iron (an annealed nail) or copper, rather than brass. Brass is nice but it shouts out "modern"